【作者】 王云；

【导师】 计建炳； 陆向红；

【作者基本信息】 浙江工业大学 ， 化学工程， 2008， 硕士

【摘要】 生物柴油是可再生的清洁能源,发展生物柴油产业是解决当前能源危机和环境污染的有效途径之一。生产成本高是制约我国生物柴油产业发展的最大障碍。为了降低生物柴油的生产成本,本文研究了一种新型、高效、节能的生物柴油生产技术。在水力空化过程中,空化泡在溃灭瞬时在其中心点会产生高温、高压,并伴随有一系列空化效应。利用该过程释放的能量和产生的特殊环境可以实现对化学过程的强化。依照此原理,本文设计了一套水力空化实验装置,以强化碱催化酯交换反应制备生物柴油。考察了在水力空化辅助条件下空化元件孔板的入口压力、醇油摩尔比、反应时间、催化剂用量、反应温度等因素对酯交换反应的影响。正交实验表明各因素影响顺序为:醇油比＞催化剂用量＞孔板入口压力＞反应时间,并确定了生物柴油制备的工艺条件:孔板入口压力为600kPa,醇油摩尔比为6∶1,催化剂KOH用量为菜籽油质量的1.0%,反应时间为20 min,反应在室温下即可进行。在此反应条件下,生物柴油产率高于99%,显著优于传统的机械搅拌。实验中共设计六种孔数与孔径均不相同的孔板,考察了空化元件孔板结构对酯交换反应的影响。结果表明,比周长、空化数是影响酯交换反应的重要参数,当过流面积一定的条件下,应优先选用孔径较小且孔数较多的孔板。考察了水力空化对醇油不溶体系的乳化、强化以及节能作用。实验表明,水力空化对对油脂与甲醇不相溶的两相有很好的乳化作用,大大地增加了两相接触面积,进而强化酯交换反应过程,是一种高效、节能的生物柴油制备技术。采用与水力空化具有相似效果的超声空化方法,对油脂和甲醇体系进行超声空化混合达到两相乳化,使用激光粒度测试仪Zetasizer 3000对酯交换过程中乳液液滴的粒径进行了测定。结果表明,空化条件下乳液液滴的平均直径为37.8nm,空化技术对醇-油体系有非常显著的乳化效果。放大试验表明,水力空化设备简单、易于实现,克服了其他强化方法难以用于强化大规模生产过程的缺点,有望将空化技术推向实际工业生产。试验制备的生物柴油性能符合我国生物柴油标准。更多还原

【Abstract】 Biodiesel is a sort of renewable fuel energy sources. Developing biodiesel industry is one of the effective ways to deal with energy crisis and environmental pollution today. High production cost is the biggest obstruction to the development of biodiesel industry in our country. This paper tries to develop a new-style, time and energy saving production technology for reducing the production cost of biodiesel.High temperature and pressure will be produced at the center point of bubbles when cavitation bubbles collapse in liquid during hydrodynamic cavitation process, accompanying with a series of cavitational effects. Because of its liberative energy and special environment, hydrodynamic cavitation can be used to intensify chemical reaction processes. Therefore, a hydrodynamic cavitation set-up was designed to intensify transesterification reaction process between rapeseed oil and methanol in this paper.The effects of inlet pressure of cavitation element, orifice plate, molar ratio of methanol to oil, reaction time, KOH amount and reaction temperature on transesterification were studied with the help of hydrodynamic cavitation. Orthogonality experiments indicate that the order of the impact factors is the molar ratio of methanol to oil > KOH amount > inlet pressure > reaction time, according to biodiesel yield. The effect of temperature on the yield was also investigated. The optimal reaction condition is 600 kPa inlet pressure, 6:1 molar ratio of methanol to oil, 1.0% KOH and 20 min. Under the optimal reaction condition, biodiesel yield more than 99% was obtained. The transesterification reaction time and yield obtained from hydrodynamic cavitation are better than that of mechanical stirring.In the present study, six kinds of orifice plates with different diameter and number of holes were used to investigate the effects of structure of orifice plates on the results of transesterification. Results shows that specific perimeter and cavitation number are the main parameters which affect the results of transesterification. If flow area is fixed on an orifice palte, many more number of holes but with smaller diameter is preferred.Futhermore, emulsification and intensification of hydrodynamic cavitation technology were considered. Hydrodynamic cavitation can emulsify oil and methanol system resulting in increasing the contact area greatly between the two phases of liquid, which lead to reaction process enhancement. Hydrodynamic cavitation is proved to be a time and energy saving method. Acoustic cavitation, which is similar to hydrodynamic cavitation, is applied to mix the oil and methanol system to make the two phases emulsify, and then particle size of emulsion drop is tested by laser particle size analyzer(Zetasizer 3000). Results indicate that the mean diameter of emulsion drop is 37.8 nm, and cavitation technology is an excellent process intensification method to emulsify oil and methanol system.The scale-up experiments indicate that the equipment of hydrodynamic cavitation is simple and reliable, and easier to be carried out in industry than other process intensification methods. The properties of the biodisel prepared from rapeseed oil are in accord with China biodiesel standard.更多还原